U.S. Pat. No. 4,508,842 discloses a highly active vanadium-containing catalyst suitable for producing ethylene polymers comprising:
(A) a solid catalyst component consisting essentially of
(1) an inorganic carrier, as support for PA1 (2) the reaction product of (a) a vanadium trihalide and (b) an electron donor, and PA1 (3) a boron halide or alkylaluminum modifier, PA1 (1) a solid, particulate, porous inorganic carrier, as support for PA1 (2) the reaction product of (a) a vanadium trihalide and (b) an electron donor, and PA1 (3) a boron halide or aluminum modifier, PA1 (1) a solid, particulate, porous inorganic carrier, as support for PA1 (2) the reaction product of (a) a vanadium trihalide and (b) an electron donor, and PA1 (3) a boron halide or alkylaluminum modifier. PA1 M is boron or AlR.sup.3 .sub.(3-a) wherein each R.sup.3 is an alkyl radical containing from 1 to 14 carbon atoms, which radicals may be the same or different, PA1 X is selected from the group consisting of fluorine, chlorine, bromine and iodine, and mixtures thereof, and PA1 a is an integer having a value of 0, 1 or 2, provided that a is 3 when M is boron. PA1 (1) the reaction product of (a) a vanadium trihalide and (b) an electron donor, and PA1 (2) a boron halide or alkylaluminum modifier. PA1 R.sup.4 is hydrogen or an unsubstituted or halosubstituted alkyl radical containing from 1 to 6 carbon atoms, which radicals may be the same or different, PA1 X' is halogen, and PA1 b is 0, 1 or 2.
(B) an alkylaluminum cocatalyst, and
(C) a halohydrocarbon polymerization promoter.
U.K. patent 1,015,054 likewise discloses vanadium-containing catalyst compositions useful in polymerizing unsaturated aliphatic compounds. Such compositions are obtained by mixing together a vanadium compound and an addition compound of an aluminum alkyl with diisopropyl ether.
According to this reference, the addition compound can be formed from equimolar amounts of the aluminum alkyl and the diisopropyl ether, but an excess of the ether is preferred as the rate of polymerization increases with the concentration of ether.
Japanese patent publication 61-126111 (Japanese patent application Ser. No. 84/248159) is yet another reference which discloses vanadium-containing catalyst compositions useful in polymerizing olefins. The catalyst compositions of this reference are prepared by combining (a) the reaction product of vanadium tetrachloride with an ether or ester with (b) an organoaluminum compound which has been modified with an ether, ester or ketone.
According to this reference, polymerization activity is enhanced by the use of such catalyst. However, this activity enhancement appears to be peculiar to vanadium tetrachloride based catalysts.